In the 1970s, the American Economic Association (AEA) was one of several professional associations to launch a summer program with the goal of increasing racial and ethnic diversity in its profession. In this paper we estimate the effectiveness of the AEA’s program which, to the best of our knowledge, is the first to rigorously study such a summer program. Using a comparison group consisting of those who applied to, but did not attend, the program and controlling for an array of background characteristics, we find that program participants were over 40 percentage points more likely to apply to and attend a PhD program in economics, 26 percentage points more likely to complete a PhD,and about 15 percentage points more likely to ever work in an economics-related academic job. Using our estimates, we calculate that the program may directly account for 17-21 percent of the PhDs awarded to minorities in economics over the past 20 years.